CLEVELAND -- Firearm evidence in police lockers that could hold the answer to unsolved violent crimes is not being routinely tested, allowing criminals to escape justice, a Channel 3 News investigation found.

In the aftermath of many shootings, the only evidence linking the gunman to the crime is a shell casing that had surrounded the slug before it was discharged.

Without a way to connect the two, such cases can quickly grow cold.

But there is a way to breathe new life into these unsolved shootings -- if only police departments would take advantage of it. It's called the National Integrated Ballistic Information Network, or NIBIN.

NIBIN works by comparing shell casings from various crimes to see if there match. If there is, detectives can use the information to develop potential suspects.

"It is a great tool," said Ohio Attorney General Mike DeWine. "It is, candidly, an under-utilized tool."

Larger cities like Cleveland, Lorain, Akron, Canton and Painesville routinely use the database. The results speak for themselves. Police in Ohio had 400 "hits" last year that linked one crime to another

But the station found that many suburban departments submit a small percentage of the guns they seize to NIBIN:

Parma: 2 percent

Lakewood: 4 percent

Westlake: 12 percent

Euclid: 13 percent

University Heights: 21 percent

Shaker Heights: 42 percent

The result is that clues to unsolved crimes murder may be locked up in evidence lockers, waiting to be discovered.

"Why wouldn't you be using the system?" asked Tara Price, whose son, Sherwon Wanzo, was murdered last year. The killer has not been found.

"You have a system that you could use. And it's a possibility that you might get a hit. So I'm very upset. I'm very disappointed."

Lakewood Police Chief Tim Malley said his department hasn't used the system because it doesn't have a "full understanding" of the program.

"We're really pretty much unaware of the program," Malley said. "Our goal is always to try to solve every crime and to prevent every crime from occurring, and if this database could do that, that's great."

Parma Police Chief Robert Miller said his department has just instituted a policy to submit guns and casings to NIBIN.

A month after Channel 3 News contacted Parma Police about NIBIN, they had a hit connecting a gun in their evidence locker to a shooting in Cleveland 7 years ago. The chief said the gun was seized from a man charged with carrying a concealed weapon.

"We can't turn the hands of time back ..., but certainly moving forward we can do a better job," said Miller.

NIBIN uses digital photos of shell casings to link violent crimes involving firearms. The shell casings can come from crime scenes or from guns seized during an arrest and later test-fired in the lab.

Like the national DNA database, NIBIN compares the shell casings with those uploaded by police agencies looking for help on their unsolved cases. Potential matches come back in a matter of hours for crime scene investigators to compare.

"The old notion that the firearms are used in a crime and then tossed in a river, those days are gone," said David Coulson, a spokesman for the U.S. Bureau of Alcohol, Tobacco and Explosives, which runs the database. "Firearms get passed along, from criminal organization to criminal."

The attorney general says he will make it a priority to make sure that police forces know about NIBIN and use it for every gun.

"I will guarantee you we will solve hundreds and hundreds of more crimes," said DeWine. "We will get criminals of the streets and we will ultimately save lives."